A laminated secondary battery, such as a lithium ion secondary battery, includes a laminated body in which positive and negative electrode plates are alternately laminated, a cell case that accommodates the laminated body therein, an electrolyte solution that fills an inside of the cell case.
Such a secondary battery is generally used as an assembled battery in which plural battery cells are accommodated in a single battery case. When used as a battery, if a temperature differential among the battery cells becomes large, a battery cell with a relatively higher temperature is charged, discharged, and deteriorates faster than a battery cell with a relatively low temperature. In addition, upon deteriorating, the battery cells may expand. The expansion of the battery cell can be sensed with a strain gage to the battery call.
The technique for sensing the expansion of a battery with the strain gage attached to a battery is disclosed in PTL 1.